Process of making large coke particles



Aug. 18, 1970 E. N. CASE.

PROCESS OF MAKING LARGE COKE PARTICLES Filed Oct. 2, l967 mp \S H. AFANNNX. H.

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A TORNEYS "United States Patent Ware Filed Oct. 2, 1967, Ser. No. 671,929 Int. Cl. C1011 55/02, 55/04 US. Cl. 208-46 22 Claims ABSTRACT OF THE DISCLOSURE Large pellets of petroleum coke, with physical properties suflicient to meet the requirements of metallurgical and chemical processing, are formed by passing a fluid, agglutinizing hydrocarbon binder material, particularly asphalt, into a compact bed of finely divided coke, so that discrete particles of the coke are bound into large pellets precursors. The binder is pyrolized, either concurrently or subsequently, to form coke, providing a discrete pellet. 'The physical properties of the calcined pellet can be enhanced by adding additional charges of the binder to the discrete pellet, with subsequent pyrolysis, until the requisite mechanical properties are attained.

This invention relates to a process for pelletizing coke. More particularly, the invention concerns a method of forming small particle size coke into larger, dense, hard pellets having the requisite physical and mechanical characteristics for use in a wide variety of applications, particularly for metallurgical and chemical processes and the like. It further relates to a method for forming small coke particles into larger, dense, hard pellets which can be roughly uniform in shape, such as, for instance, spherical, hemispherical, or hemicylindrical.

The two most common types of petroleum coke are formed in the delayed coker process and the fluid coking process. In the delayed coking process, which has been long known, coke is formed during thermal cracking of a topped crude or residual stock and deposited on the interior walls of vessels, known as coke drums. For most uses the raw coke in finely divided form is devolatilized by calcining. Calcined delayed coker coke is not mechanically suited for many applications.

Fluid coke is prepared by a relatively recently commercialized continuous, fluidized-solid process also involving the thermal conversion of heavy hydrocarbon oils to lighter fractions. A feedstock, usually a heavy residual stock, is dispersed in a fluidized coke bed at elevated temperature, for instance, about 900 to 1,000 F. Thermal conversion products, including gases and distillates of wide boiling point range, leave the reactor as overhead vapors. A portion of the charge, e.g. about 5 to 25%, is converted to coke which is deposited on the fluidized coke particles already in the reaction zone, but the coke particles separated as product are still of relatively small size. Fluid coke is, like delayed coke, unsuited for many applications.

It is well known to produce pellets from either fluid or delayed coke by mixing the coke with a hydrocarbonaceous binder capable of forming coke and subjecting the mixture to either an extrusion or a molding process followed by calcination to convert the binder to coke. In other conventional processes, hot fluidized coke is coated with a binder material and compacted into pellets or briquettes by the application of high temperature and mechanical compression. Hard, compact pellets are often formed by charging the coke-binder mixture to a rotating drum for balling, which subjects the mixture to a rolling motion on a horizontally rotated surface. Pellets may also be formed by extruding the mixture. Briquettes can be formed in a hydraulic press at a pressure of about 10 to 25,000 p.s.i., ordinarily 2,000 to 10,000 p.s.i. The coke pellets or briquettes formed by these processes lack suflicient hardness and mechanical strength for metallurgical or other processes where coal coke is ordinarily required. Moreover, these pellet-forming operations are relatively expensive and therefore undesirable.

Thus, it is an object of this invention to provide a process whereby petroleum coke may be formed into relatively large pellets having the requisite physical and mechanical properties for metallurgical and chemical processing which require high density and high mechanical strength. It is a further object to provide a method for producing such coke pellets without reliance upon elaborate mixing and forming operations and without elaborate equipment requirements. These and other objects are realized by the process of the present invention.

The process of the present invention provides a method for producing large, hard pellets of coke which may be roughly of uniform shape and size. This method comprises adding a liquid, coke-forming hydrocarbon binder material to a compact bed of small particle size coke, preferably delayed coke, under conditions that the binder penetrates the bed to the extent required to form a pellet of desired size, and calcining the pellet to pyrolyze the binder to coke. The present process eliminates the necessity for mechanically mixing the binder and the coke and equipment for conducting the mixing and also avoids the requirement for extrusion or high pressure molding equipment to form pellets of uniform shape and size.

The process of the present invention takes advantage of the phenomenon of capillary flow of liquids in finely divided, Wettable solids. Thus, in the instant process, the binder is added to a bed of coke under conditions such that the binder is a liquid and will pass readily into the bed by capillary flow. The bed must be large and deep enough to absorb all the binder by capillary flow. Ordinarily, all that is required to produce capillary flow of the binder is to maintain elevated temperature, that is, a temperature at which the binder is liquid, for sufficient time for the liquid to flow through the desired portion of the bed. Since capillary flow is the primary force involved in the penetration of the fluid into the bed, the liquid will advance more or less uniformly from the point of addition to the limit of the volume of the liquid. At the point of addition of the liquid binder, there may be a temporary local flooding of the coke bed. The binder will then flow uniformly outward from the point of addition by capillary flow into dry areas of the bed. Thus the binder will form an advancing front of liquid, moving by capillary flow, which front will be characterized by wetting of the bed by capillary flow at the locus of the front. When the flow continues until the binder is completely distributed, the liquid will be located primarily at the junction points of adjoining particles in the bed. Surface tension causes the liquid to wet the solids at these points and the forces of the liquid causes the coke mass to contract so there is firm particle to particle contact, increasing the apparent density of the mass. The surface tension holds the liquid at these contact points and prevents the liquid from filling the void spaces ordinarily associated with a packed solid. The liquid front Will continue to advance into the surrounding dry bed until the liquid material is all distributed and there results a volume of solids wet with the liquid binder bounded by dry coke. The dry coke boundary defines the limits or size of the binder-wetter coke pellet precursor.

The shape of the pellet precursor will be determined by the manner of addition of the binder. Since the liquid binder advances more or less uniformly through the bed, the pellet will be a relatively uniform spherical shape if the binder is added to the bed at a single point within the bed. If the point of addition is on the surface of the bed, penetration will, of course, give a roughly hemispherical shape. If the binder is added along a line, or a number of points along a line, a cylindrical or hemicylindrical shape will result.

The size of the pellet precursor is a function of the amount of the coke-forming binder added to the bed, so long as conditions are maintained so that the binder material is allowed to wet the binder by capillary flow to the maximum. Maximum fiow can be impeded by allowing the system to cool until the viscosity of the binder increases to the point at which capillary flow will no longer occur. Also maintenance of too high a temperature may result in premature coking or loss of volatiles from the binder so that capillary flow is blocked by increased viscosity of the binder.

The unwetted coke often has about 65% void space by volume in the compact bed. When the coke-forming binder is added and allowed to fiow to its maximum penetration by capillary flow, there can still be about to 40% by volume void space. This is because the surface tension at the particle interfaces forms a greater attraction for the liquid than does the void space. Thus, the pellet precursor can be calcined to convert the binder to coke without disrupting the structure of the pellet, since the gases produced in the coking step escape from the interior of the pellet through the voids. Calcining reduces the volume of the binder and in the pellet thus formed the void space can be increased to about 55 to 60 percent by volume or somewhat less.

The binder of the present invention may be any agglutinizing hydrocarbonaceous material which may be converted to coke at high temperature. The binder must be fluid at the temperature of addition to the bed of coke, and is preferably a material which gives a high coke yield per unit volume. Thus the binders include the various hydrocarbonaceous coking feedstocks, for example, asphalt and other heavy petroleum residuals, petroleum pitches, clarified oils, aromatic petroleum extracts, aromatic tars, heavy ends of coal tars such as coal tar pitch, and heavy ends from a coking operation, and the residue resulting from the propane extraction of such materials, usually boiling primarily above about 900 F. and preferably being normally solid at room temperature. Particularly desirable binder materials include asphalts, which may be soft, medium, or hard grade asphalts. Soft grade asphalts are ordinarily characterized by a penetration of about 200 to 300 and a furol viscosity at 275 F. of about 100; medium grade asphalts are ordinarily the materials having a penetration of about 60 to 70 and a furol viscosity at 275 F. of about 200; and hard grade asphalts usually have a penetration of about 20 to and a furol viscosity at 275 F. of about 300. A particularly preferred binder material comprises the residue from the propane extraction of an asphalt, especially a residue having a penetration of about 20 to 60 and a furol viscosity at 275 F. of about 375.

The foregoing steps of the present process, i.e., adding the binder to the coke bed and calcining the resulting pellet precursor, can be carrier out in a number of ways. For instance, if the binder is added to a hot bed of coke, the capillary flow and pyrolysis of the binder can occur concurrently if the temperature is maintained high enough to cause pyrolysis. On the other hand, these steps can be conducted separately by adding the binder at a temperature high enough to produce fairly rapid capillary flow in the bed but below the temperature at which substantial coking will occur, for instance, from about 300 to about 850 F. Once the binder charge is distributed through the coke, the pellet precursor can be calcined to pyrolyze the binder. Combination of such operations can also be used.

The desirable binder materials of various types previously mentioned are ordinarily solids or very viscous liquids at ambient temperatures but become quite fluid at elevated temperatures on the order of about 300 to 700 F. Thus, if the binder material, heated to about 300 to 700 F. to obtain a desirably low viscosity, is added to a compact bed of small particle form coke similarly heated, the binder will flow by capillary action into the bed relatively rapidly. The result of such flow will be a pellet precursor, comprising a volume of coke, wetted by the binder, and bounded by unwetted coke. The shape of the pellet precursor Will be determined by the aforementioned manner of addition of the binder. If the pellet precursor, prepared as described above without substantial coking of the binder is allowed to cool undisturbed to substantially ambient temperature, the binder will revert to its original highly viscous condition. The combination of the very close packing of the coke particles and the high viscosity and adhesive character of the binder plus perhaps a minor amount of coking, will make the pellet precursor structurally quite stable. In the case of an asphalt binder, for example, the pellet precursor has been bounced on the floor without deformation. If the pellet precursor is simply heated to pyrolyze the binder, the structural integrity can be lost as the viscosity of the binder decreases and the shape is destroyed. If, however, essentially the entire perimeter of the pellet precursor is supported during heating, as for example, if it is buried in a compact bed of small particle coke or other small, inert particles, the binder will pyrolyze more or less completely, leaving a coke residue which binds the coke particles in the pellet. Thus a hot bed of coke or sand can serve both as an inert heat exchange medium and as a support for the pellet while it lacks structural integrity. The support bed and the pellet can be readily separated at the conclusion of the pyrolysis to give a pellet which can be the same size and shape as the pellet precursor. It is preferred that the support medium be coke, so that contamination of the pellet with extraneous material does not occur, particularly if the amount of binder in the precursor is sufficient to cause growth of the pellet during pyrolysis due to migration of the binder into the surrounding bed. It is also preferred that the support medium be predominantly of a particle size of about 10 mesh or finer.

Calcination may be conducted at any temperature at which the binder will pyrolyze to form coke. Ordinarily, the temperature will not exceed about 2000 F., and preferably will be not greater than about 1300 F., and will generally be at least about 850 F. or 900 F.

The pellets thus formed, i.e. by more or less simultaneous or by sequential forming and pyrolysis, have some strength, but not enough to be of use as, for instance, metallurgical coke. Such pellets also have considerable porosity, as mentioned above. The porous nature of the pellets makes it possible to increase the strength of the pellets very simply by adding a second charge of hot binder to the heated pellet so that the fluid binder permeates the pellet, preferably again by capillary flow, to avoid growth of the pellet which occurs if more binder is added than can be accommodated by capillary flow. Such growth is not always undesirable, but is not ordinarily necessary to the process. A second calcination pyrolyzes the second binder charge to provide additional coke residue which substantially increases the mechanical strength. It is possible by alternately adding binder material to the porous aggregate and pyrolyzing the binder by calcination to substantially increase the strength of the original pellet. During the second and subsequent calcinations the pellets need not be supported in a bed of finely divided solids but may be calcined by any convenient means. While complete filling of the void spaces Within the pellet may not be desirable, it is possible to obtain a pellet which has about 10% or even less void spaces. The degree of filling of the voids will depend on the mechanical strength required of the final pellet for a particular use.

The beds of small particle form solids employed in the pellet forming and baking operations of this invention are compact beds of such solids. Rebaking can also be done in this type of bed. By the designation compact is meant that adjacent particles of the bed are in essentially static contact with one another, although the bed can, if desired, be moving progressively, for instance, in a downwardly direction. During such movement the particles of the bed remain in essentially the same relative position with one another as in conventional moving bed processes. Also, the bed is sufiiciently dense that the pellets of coke do not pass or move through the bed but rather retain their relative position with respect to the surrounding dry particles of the bed. Normally, little, if any, gas flows through the bed except for volatiles that are given off from the binder material, and, in any event, such gas does not destroy the compact nature of the bed. The small solid particles in the bed are often less than about mesh. Finely divided materials such as ground delayed coke are particularly advantageous.

The coke formed in the calcination of the binder in the pellet precursor or in reinforcing already formed pellets has essentially the same structure as delayed coke and it is for this reason that it is preferred to use delayed coke in forming the pellets. If the coke in the finished pellet is entirely of the same structure, more uniform burning rates during use will occur. When fluid coke is used, the coke derived from the binder burns preferentially, resulting in a non-uniform burning rate and possibly early particle collapse.

If, prior to addition of the initial binder, the coke bed is heated and maintained at a temperature at Which pyrolysis will occur, the binder will be pyrolyzed more or less concurrently with the flow into the coke bed. It is important that the temperature not be too high or binder volatiles will be lost rapidly and coking may occur too fast with the binder becoming too viscous to flow and the bed being flooded. Flooding of the bed at coking temperatures can cause boiling or bubbling of the binder and consequent disruption of the structure of the pellet by the action of the gases evolved from the binder during pyrolysis. The gases are not able to escape readily from the flooded area because of the blockage of the voids due to the flooding of the bed. From a practical point of view, when coking is desired while forming the pellet, the temperature of the bed should be at least about 850 F., since below this temperature, coking may not occur at a reasonable rate. At temperatures above about 1100 F., coking can be so rapid that the binder may not penetrate the bed more than about an inch. Ordinarily, a temperature within the range of about 900 to 1000" F. is preferred when it is desired to calcine the pellet concurrently with the addition of the binder. Flooding of the bed will also occur if the binder material is added to the coke at a rate much greater than it will flow by capillary action, and, as stated, flooding is disadvantageous when coking is effected during pellet formation.

While the concurrent binder addition and calcination requires more control, i.e., maintenance of both temperature and flow rates, in order to insure the capillary flow required, the operation benefits both by utilizing only a single step in forming the initial pellet and the elimination of handling of the relatively more fragile pellet pre cursor often required in the separate binder addition and calcination steps. Moreover, the size of the pellet is restricted by the high temperature of the concurrent binder addition and calcination or coking operation. As the binder is pyrolyzed at the high temperature, the viscosity increases rapidly and capillary flow is impeded. The limit of penetration of the dry coke bed by the fluid binder is a function of the rate of coking, which in turn is directly dependent on the temperature of the system. At temperatures above about 1100 or 1200 F., coking is so rapid that penetration is limited. At more desirable lower temperatures, the size of the pellet will be proportionately larger. For instance, at about 1000 F., penetration can be up to about 4 inches, while at about 900 F., about 12 inches of penetration by capillary flow can be obtained. At lower temperatures, i.e., below the temperature at which coking will occur at an appreciable rate, the size of the pellet is not so restricted. The pellets made by this invention are usually at least about 0.5 inch in cross-section preferably at least about 1 inch.

In any event, the initial pellet, however formed, will have only limited mechanical strength and may consequently be unsatisfactory for many uses, such as metallurgical coke. It will often be desirable to increase the strength as described above, by subsequent additions of binder followed by calcination.

The instant invention is further illustrated with reference to the appended drawings in which FIG. 1 is a schematic view of the process of the instant invention wherein binder addition and calcination occur simultaneously, and

FIG. 2 is a schematic view of the process of the instant invention wherein binder addition and calcination occur separately.

Referring now to FIG. 1, a vertical furnace 1 is charged with a compact bed 2 of finely divided coke. The furnace l is heated by suitable heating means indicated generally as 3. The coke bed 2 is heated in the furnace area generally indicated as 4. The compact bed 2 is moved along the furnace by gravity. A binder injection means 5, shown as a tube, centrally located within furnace ll injects binder into the coke. As noted before, a single injection means forms a generally spherical pellet 6. The pellets, within the compact bed of unbound coke particles, are calcined in the furnace in the area subsequent to binder addition generally indicated as '7. After calcination, the pellets 6 are separated by any suitable separating means and can be transferred into another furnace similar to furnace 1 for further binder injection and calcination or transferred to a storage area (not shown), for later processing or transferred to a suitable packaging area for packaging for delivery to the ultimate user.

FIG. 2 shows another embodiment of the invention in which the compact coke bed 2' in furnace 1' is preheated in the furnace area designated as 4'. Furnace heating means are designated generally as 3'. The coke bed 2 is injected with binder introduced through injection means 5' to form generally spherical pellets 6 which are then transferred to a cooling area, generally designated as 7, which is cooled by suitable furnace cooling means 8 After cooling, the pellets 6 are separated from the coke bed 2'. The pellets 6' are then inserted in a suitable bed of particles 9 and transferred to calcination furnace 10' heated by suitable means 11. After calcination, the calcined pellets are separated from the bed of particles 9' and reprocessed or stored as before.

The following examples serve to illustrate the operation of the process of the present invention. While particular apparatus is described, it forms no part of the present invention and should not be construed as limiting the invention. This invention contemplates the operation of the disclosed process in any desired manner.

EXAMPLE I Two coke beds, designated the pelletizer and the calciner, respectively, were provided as follows:

The pelletizer consisted of a heater section where the finely divided coke was preheated to a temperature of about 350 to 400 F. The heated coke was then passed as a downwardly moving compact bed into a cylindrical injection zone about 2 inches in diameter by about 4 inches in length. Inside the cylindrical section there was centered a /8 inch tube which terminated midway down the bed through which the binder, preheated to a temperature of about 400 to 600 F., was introduced into the compact bed of coke. The chosen binder in the present examples was asphalt of about 200 to 300 penetration at 77 F. Below the injection zone an additional cylindrical section was provided which served as a cooling zone. The cooling zone was about 2 inches in diameter by about 3 feet in length and was water-jacketed to provide for heat removal. Mechanical means were provided to alternately move the coke bed downwardly through the injection and cooling zones in increments of about 3 inches at a time and to inject the asphalt binder into the bed. Thus, in operation, asphalt binder was added to the stationary bed of hot coke and the bed was then lowered for a fresh injection of binder into a dry portion of the bed. The coke was replenished at the top as the level dropped and pellet precursors were continuously removed at the bottom of the cooling zone.

The calciner unit was made up of a 3 foot long by 2 inch diameter cylindrical heating zone to heat a compact bed of finely divided carrier coke to above calcination temperature, provided with an additional 5 foot long feed cylinder 3 inches in diameter open at the top to permit introduction of the pellet precursors to be calcined and to receive dry, preheated coke for support and as a medium of heat transfer. Mechanical means were provided to move the pellet precursors and the supporting coke continuously downwardly. The pellets were heated in the heating zone to a temperature of about 900 to 1000 F. to pyrolyze the asphalt binder to coke.

Delayed coke was ground in one pass fine enough that about 80% would pass a mesh screen. This coke was introduced to the pelletizer and heated to about 350 to 400 F. as a compact bed. :Each of the pellet precursors was formed by injecting about 3 grams of hot asphalt at about 400 to 600 F. into the dry coke in a period of about seconds. The pellet precursors recovered from the pelletizer were spheres, typically about 1.5 inches in diameter and about 14.2 grams in weight. The pellet precurosors were then introduced to the calcining unit where they traversed the heating zone in about 30 minutes at a temperature of about 900 to 1000 F. The calcined pellets recovered were the same shape and size as their precursor, but weighed only about 12 grams.

The initial 12.0 gram pellet from the calciner was treated with an additional increment of the asphalt of 4.2 grams, representing of the weight of the pellet. Pellet and added binder thus weighed 16.2 grams. The pellet was again introduced into the calciner and the binder was pyrolyzed to give a pellet weighing 13.1 grams. To this pellet was added 25% of its weight (3.3 grams) of asphalt to give a pellet of 16.4 grams which was again pyrolyzed to give a final weight of 13.9 grams; the final pellet was suitable for use as metallurgical coke.

Examples II through V are presented to illustrate the process of the present invention embodied in the concurrent binder addition and pyrolysis.

EXAMPLE II A circular compact bed of finely divided coke of Example I, 24 inches in diameter and 6 inches deep was rotated under an orifice GA copper tube) from which asphalt was added continuously to the bed. The asphalt was preheated to 400-500 F. to facilitate pumping. The coke surface to which the asphalt was added passed the orifice at approximately 200 feet/min. Under these conditions three runs were made with the coke at different temperatures to provide roughly toroidal pellets, the toroidal shape being semicircular in cross-section.

duced due to lack of penetration. In the third run the center of the coke pellet was missing as the result of the boiling of the binder. At this high temperature the coking took place so rapidly that the coke bed at the junction of liquid and hot dry coke is sealed off, thus the gases must pass through a liquid mixture of uncoked asphalt and unconsolidated coke, and the structure of the pellet is disrupted.

EXAMPLE III In forming pellets at 900 F., the following runs illustrate the effect of feed rate in relation to the rate of capillary flow of the binder into the coke bed. The coke was a fluid coke of smaller size than 28 mesh having approximately in the 60 to 200 mesh range. The operating procedure was the same as in Example II.

Rate of Size of Pellet Feed in addition, Yield,

grams grams/min. grams Width Depth 55 668 1 x M 100 9 335 1 X }6 500 55 2,710 2 x 1% 500 9 781 x 482 107 2, 226 4 x 1 Comparison of the first two runs indicates that in the first run there was sufficient asphalt to maintain an essentially continuous flow into the bed of coke. The second run indicates that there was insuificient asphalt to maintain a wet bed. Consequently, portions of the bed dried out between passes under the orifice, and each increment added made only a partial penetration. This is shown by both a decreased depth of penetration and decreased yield. Comparison of runs 3 and 4 shows the same trend, but also indicates that the coke bed can consume at least 500 g. of asphalt at appropriate rates of addition.

Run 5 shows the effect of adding asphalt to the coke bed at a rate faster than it can penetrate by capillary action. While the yield is quite similar to No. 3, the pellet was very wide and thin indicating there was substantial lateral flow of the asphalt across the surface of the bed.

EXAMPLE IV To demonstrate the effect of successive treatments on the strength of the resulting pellets the following tests were conducted.

A series of coke pellets weighing 14 to 16 grams each was made by the addition, under non-flooding conditions, of two grams (for each pellet) of an asphalt-binder material heated to 400 to 500 F. to facilitate pumping, to the surface of a compact bed of finely divided coke particles maintained at a temperature of about 900 F. The asphalt flowed into the bed to form hemispherical pellets while coking of the asphalt occurred. One of the pellets which were approximately 1.5 inches in diameter, was saturated with the asphalt and rebaked at 950 to 1,000 F. Another pellet was saturated, baked, saturated a second time, and baked again. Cubes of each pellet were cut, measured, and crushed in an hydraulic press to determine strength. An original pellet, crushed at 615 p.s.i., the first rebaked pellet crushed at 1,059 p.s.i., and the doubly rebaked pellet crushed at 3,619 p.s.i. These experiments illustrate the increase in strength by Asphalt added Pellet, inches Comparison of these three runs shows that as the temperature is increased penetration into the bed is decreased because coking is more rapid and the binder rapidly increases in viscosity. The weight of the pellet is also reprogressively filling the void space between the spherical pellets of fluid coke. In comparison, typical blast furnace coal cokes have crushing strengths of about 1,300 p.s.i. for a poor grade to as high as 3,000 p.s.i. for exceptional- 1y hard coke. An average blast furnace coke tests about 2,000 psi. in crushing strength.

In a second series of such tests, a number of pellets of approximately 16 grams each and hemispherical in shape and measuring 1 /2 inches by inch were similarly prepared including the double rebaking procedure. The pellets were subjected to a simulated drop test to determine the shatter index as is done with metallurgical coke used in steel mills. The index is expressed as percent of the sample remaining greater than 1 inch and percent greater than 2 inches after 3 drops onto a steel plate from a height of six feet. The pellets tested showed an index of 99.5% plus 1 inch whereas a good grade of blast furnace coke will show 80% plus 2 inches and 96% plus 1 inch. None of the pellets dropped showed any breakage and any loss was due to a small amount of dusting at the point of impact at each drop.

EXAMPLE V To demonstrate the effect of coke bed temperature on the process, the following tests were made.

A pellet of asphalt was placed on a compact bed of finely divided coke preheated to 800 F. After two hours at this temperature the asphalt had melted and penetrated the bed, but the pellet was still relatively soft because of incomplete coking of the asphalt. A similar experiment made with a bed preheated to 800 F. but then raised to 1000 F. produced substantially complete coking of the asphalt in one hour.

It is claimed:

1. A method of making relatively large particles from smaller particles form coke which comprises forming a compact, dry, heated bed of said smaller coke particles, which particles are in essentially statisc contact with adjacent particles, adding to said bed a coke-forming heavy hydrocarbon in the liquid state to travel by capillary flow through only a portion of said bed, said portion having a cross-section of at least'about 0.5 inch and being bounded by dry particles of said bed, said addition and flow serving to wet and bind said portion of said bed as a large particle precursor, calcining said precursor while supported in a compact bed of small particle solids maintained at coking temperature to pyrolyze the heavy hydrocarbon to coke and provide said large particles, said binding and calcining being conducted without addition of a gas.

2. The method of claim 1 in which the heated bed of small coke particles is at coking temperature during formation of the large particle precursor and serves to calcine the heavy hydrocarbon to cake.

3. A method of making relatively large particles from smaller particle form coke which comprises forming a compact, dry bed of said smaller coke particles, which particles are in essentially static contact with adjacent partices, adding to said bed a coke-forming, heavy hydrocarbon in the liquid state, said bed being at a temperature below which substantial coking of the heavy hydrocarbon occurs but at a temperature sufiicient to keep the hydrocarbon in the liquid state while said heavy hydrocarbon travels by capillary flow through only a portion of said bed, said portion having a cross-section of at least about 0.5 inch and being bounded by dry particles of said bed, said addition and flow serving to wet and bind said portion of said bed as a pellet precursor, subsequently calcining said precursor while supported in a compact bed of small particle solids maintained at coking temperature to pyrolyze the heavy hydrocarbon to coke and provide said large pellets, said binding and calcining being conducted without addition of a gas.

4. The method of claim 1 in which the coke particles of the bed are less than about mesh in size.

5. The method of claim 4 in which the large particles are at least about 1 inch in cross-section.

6. The method of claim 5 in which the heavy hydrocarbon is normally solid.

7. The method of claim 2 in which the coke particles of the bed are less than about 10 mesh in size.

8. The method of claim 7 in which the large particles are at least about 1 inch in cross-section.

9. The method of claim 5 in which the coking temperature is about 900 to 1000 F.

10. The method of claim 9 in which the heavy hydrocarbon is normally solid.

11. The method of claim 3 in which the coke particles of the bed to which said heavy hydrocarbon is charged are less than about 10 mesh in size.

12. The method of claim 3 in which the compact bed employed for calcination is composed of coke particles of less than about 10 mesh in size.

13. The method of claim 12 in which the large particles are at least about 1 inch in cross-section.

14. The method of claim 13 in which the heavy hydrocarbon is normally solid.

15. The method of claim 14 in which the first coke bed is at a temperature of about 300 to 850 F. and the second coke bed is at a temperature of about 900 F. to 1300 F.

16. The method of claim 1 in which the strength of the large particle is increased by adding a coke-forming heavy hydrocarbon to the calcined, large particle and calicining the particle to pyrolyze the heavy hydrocarbn to coke.

17. The method of claim 2 in which the strength of the large particle is increased by adding a coke-forming heavy hydrocarbon to the calcined, large particle and calcining the particle to pyrolyze the heavy hydrocarbon to coke.

18. The method of claim 3 in which the strength of the large particle is increased by adding a coke-forrning heavy hydrocarbon to the calcined, large particle and calcining the particle to pyrolyze the heavy hydrocarbon to coke.

1.9. The method of claim 6 in which the strength of the large particle is increased by adding a cokeforming heavy hydrocarbon to the calcined, large particle and calcining the particle to pyrolyze the heavy hydrocarbon to coke.

20. The method of claim 10 in which the strength of the large particle is increased by adding a coke-forming heavy hydrocarbon to the calcined, large particle and calcining the particle to pyrolyze the heavy hydrocarbon to coke.

21. The method of claim 14 in which the strength of the large particle is increased by adding a coke-forming heavy hydrocarbon to the calcined, large particle and calcining the particle to pyrolyze the heavy hydrocarbon to coke.

22. The method of claim 15 in which the strength of the large particle is increased by adding a coke-forming heavy hydrocarbon to the calcined, large particle and calcining the particle to pyrolyze the heavy hydrocarbon to coke.

References Cited UNITED STATES PATENTS 1,605,378 11/1926 Sperr 208106 1,906,863 5/1933 Knowles et al 20846 3,249,528 5/1966 Allred 20846 3,271,268 9/1966 Allred 201-25 3,285,847 11/1966 Scofield et a1. 208--46 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 

